Add optional inbound relay (backup-MX) behind INBOUND_RELAY_ENABLE.

Port 25 accepts only configured domains and listed recipients, then forwards to an upstream; the outbound path is unchanged when the flag is off.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/inbound/service.go

@@ -0,0 +1,156 @@
+// Package inbound owns backup-MX / relay-forwarder domains: the SQLite
+// registry and the Postfix lookup tables (relay_domains, transport_maps,
+// relay_recipient_maps, smtp_tls_policy_maps). It does not listen on port 25
+// itself — postfix-config.sh does that when INBOUND_RELAY_ENABLE is true.
+package inbound
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/mixeme/selfpost/internal/postfix"
+	"github.com/mixeme/selfpost/internal/store"
+)
+
+// Maps is the slice of the Postfix manager the inbound service needs.
+type Maps interface {
+	RebuildInboundMaps(routes []postfix.InboundRoute) error
+}
+
+// Service coordinates inbound-domain state across SQLite and the Postfix maps.
+type Service struct {
+	store *store.Store
+	maps  Maps
+}
+
+// NewService builds the inbound service over the shared store and Postfix maps.
+func NewService(st *store.Store, maps Maps) *Service {
+	return &Service{store: st, maps: maps}
+}
+
+// List returns every inbound domain.
+func (s *Service) List() ([]store.InboundDomain, error) {
+	return s.store.ListInboundDomains()
+}
+
+// Get returns one inbound domain by id.
+func (s *Service) Get(id int64) (store.InboundDomain, error) {
+	return s.store.GetInboundDomain(id)
+}
+
+// Add validates the domain name, inserts it, and rebuilds the maps.
+func (s *Service) Add(name string) (store.InboundDomain, error) {
+	name = normalizeDomain(name)
+	if err := checkDomain(name); err != nil {
+		return store.InboundDomain{}, err
+	}
+	d, err := s.store.AddInboundDomain(name)
+	if err != nil {
+		return store.InboundDomain{}, err
+	}
+	if err := s.Resync(); err != nil {
+		_ = s.store.DeleteInboundDomain(d.ID)
+		return store.InboundDomain{}, err
+	}
+	return d, nil
+}
+
+// SetTransport validates and saves the upstream, then rebuilds the maps.
+func (s *Service) SetTransport(id int64, host, portRaw, tlsMode string) error {
+	if _, err := s.store.GetInboundDomain(id); err != nil {
+		return err
+	}
+	host = normalizeHost(host)
+	if err := checkHost(host); err != nil {
+		return err
+	}
+	port, err := parsePort(portRaw)
+	if err != nil {
+		return err
+	}
+	if err := checkTLSMode(tlsMode); err != nil {
+		return err
+	}
+	if err := s.store.UpdateInboundTransport(id, host, port, tlsMode); err != nil {
+		return err
+	}
+	return s.Resync()
+}
+
+// SetRecipients validates the mode and, in list mode, every address, then
+// rebuilds the maps.
+func (s *Service) SetRecipients(id int64, mode string, rawAddresses []string) error {
+	d, err := s.store.GetInboundDomain(id)
+	if err != nil {
+		return err
+	}
+	if err := checkRecipientMode(mode); err != nil {
+		return err
+	}
+	var addrs []string
+	if mode == store.RecipientModeList {
+		addrs, err = parseRecipientAddresses(rawAddresses, d.Name)
+		if err != nil {
+			return err
+		}
+	}
+	if err := s.store.UpdateInboundRecipients(id, mode, addrs); err != nil {
+		return err
+	}
+	return s.Resync()
+}
+
+// Delete removes the domain and rebuilds the maps.
+func (s *Service) Delete(id int64) error {
+	if err := s.store.DeleteInboundDomain(id); err != nil {
+		return err
+	}
+	return s.Resync()
+}
+
+// Resync rebuilds the inbound Postfix maps from SQLite.
+func (s *Service) Resync() error {
+	list, err := s.store.ListInboundDomains()
+	if err != nil {
+		return err
+	}
+	routes := make([]postfix.InboundRoute, 0, len(list))
+	for _, d := range list {
+		full, err := s.store.GetInboundDomain(d.ID)
+		if err != nil {
+			return err
+		}
+		routes = append(routes, postfix.InboundRoute{
+			Domain:        full.Name,
+			Host:          full.Host,
+			Port:          full.Port,
+			TLSMode:       full.TLSMode,
+			RecipientMode: full.RecipientMode,
+			Recipients:    full.Recipients,
+		})
+	}
+	return s.maps.RebuildInboundMaps(routes)
+}
+
+func parseRecipientAddresses(raw []string, domain string) ([]string, error) {
+	seen := make(map[string]bool)
+	out := make([]string, 0, len(raw))
+	for _, r := range raw {
+		addr := strings.ToLower(strings.TrimSpace(r))
+		if addr == "" {
+			continue
+		}
+		if err := checkMailbox(addr, domain); err != nil {
+			return nil, err
+		}
+		if seen[addr] {
+			continue
+		}
+		seen[addr] = true
+		out = append(out, addr)
+	}
+	if len(out) == 0 {
+		return nil, fmt.Errorf("listed-recipients mode requires at least one address")
+	}
+	return out, nil
+}